This invention relates to ventilation systems and more particularly to auxiliary systems provided in underground mine roadways and the like situations to supplement the primary ventilation therein.
It is essential that adequate air ventilation is provided when driving underground roadways particularly at and adjacent a face being mined, and it is now common practice for the primary ventilation provided by large suitably-positioned fans to be supplemented by auxiliary ventilation systems.
Such auxiliary ventilation systems usually consist of a first fan remote from the mined face to which is attached a first length of ducting extending to the face, air being forced through said ducting to ventilate the region of said face.
As well as ventilating the face, it is sometimes necessary to remove the dust therefrom, and accordingly auxiliary ventilation systems usually further consist of a second suction fan remote from the face to which is attached a further length of exhaust ducting extending from the face.
However, as the roadway progresses and the mined face proceeds away from the fans, it becomes necessary to extend both the first and further lengths of ducting to maintain adequate ventilation and dust suppression at the face.
Although the first length of ducting through which air is being forced, can comprise lay-flat tubing--i.e. non-reinforced, smooth-faced cylindrical tubing--the further length of ducting, being for exhaust purposes, must be the more expensive rigid or spirally-reinforced pvc-type tubing. Thus the cost of extending the ventilation ducting as the face proceeds can be substantial, while the inconvenience of having to extend two separate lengths of ducting will be readily appreciated.
It has been proposed to reduce these and other problems in such underground application by providing an air box within the auxiliary ventilation system for location at or adjacent a face and which only requires the addition of one extra length of ducting (which length my itself consist of a series of interconnected units of ducting) as a face proceeds but which enables the maintenance of adequate ventilation and dust suppression at the face.
More particularly, such a box includes a pair of communicating chambers therein, one chamber having an inlet port thereto to which is connected said first length of forcing ducting and an outlet port therefrom for ventilating air, and the other chamber having an outlet port to the same side of the box as the inlet port to the one chamber and to which is attached an exhaust fan, and an inlet port thereto through which dusty air from the face being mined can be drawn by said fan.
Each chamber has mounted therein a flap, said flaps being movable between first and second positions within their associated chambers. In their first positions, the flap in the one chamber seals off a communicating aperture between the two chambers while the flap in the other chamber is in an inoperative position, the arrangement being such that ventilating air can flow straight through the one chamber from the inlet port to the outlet port thereof, while exhaust air and dust can be drawn to flow straight through the other chamber from the inlet port to the outlet port thereof, the two chambers being sealed off one from the other.
On movement of the flaps to their second positions, the inlet to the one chamber is interconnected with the inlet to the other chamber by way of the communicating aperture between the two chambers, the outlet port from the one chamber and the outlet port and exhaust fan from the other chamber being redundant, whereby the only air flow path through the box is from one inlet port to the other inlet port. Thus ventilation can be achieved by forcing air from the inlet port to the one chamber and out of the inlet port to the other chamber, although the facility for exhausting air from the ventilated area is eliminated.
Initially, the above described air box is located adjacent a face being mined and the flaps are located in their first positions to enable ventilation and exhaust to be effected. As the face proceeds, spirally-reinforced or rigid ducting is attached to the inlet port to the other chamber to extend from the box to the face whereby dust can still be removed from the face while ventilating air continues to be emitted from the outlet port from the one chamber in sufficient quantity to effect ventilation at the face.
When the level of dust at a face is acceptable, such as when the machine is not cutting and during periods of inactivity at the face at weekends, the provision of exhaust facilities becomes unnecessary. Thus the flaps can be moved from their first positions to their second positions to effect a ventilating passage through the box from the one inlet port to the other inlet port and effective ventilation at the face can take place.
Thus it will be appreciated that the provision of such an air box reduces the additional ducting required as a face progresses, whilst still enabling effective ventilation of the progressed face at times when there is no dust problem. At other times, dust suppression is effected in combination with ventilating air being emitted at the region of the box itself. Periodically it will be necessary to move the air box and associated equipment and ducting bodily nearer the face to ensure adequate ventilation at said face.
A major disadvantage of the above-detailed known air box is the means by which the flaps are moved between their first positions and their second positions. More particularly each flap comprises a rectangular member in a square-section bore and is pivoted about its lower region which is located on the base of the associated chamber, the flaps being interconnected by a pivotal link extending between the flaps. The flaps are urged into their first positions by a heavy weight acting thereon, movement to the second positions being effected by an electrically-controlled hydraulic thrustor which acts against the weight to raise said weight and pivot the flaps. On de-activation of the thrustor, the weight falls under gravity and returns the thrustor and the flaps to their initial positions.
Clearly the use of a weight and a thrustor together with the associated ancillary equipment, all of which are bulky, adds to the size of the air box, while the presence of electrical power packs and mineral oil for the thrustor at a face can lead to potentially dangerous situations arising. Further, this known air box relies on a deadweight falling under gravity to return the flaps to their initial positions and therefore requires a vertical setting of the air box before correct operation will take place.